1. Technical Field of the Invention
The present invention relates to a mask, a substrate with a light reflecting film, a method for manufacturing a light reflecting film, an optical display device, and an electronic apparatus, and more specifically, it relates to a mask for manufacturing a substrate with a light reflecting film generating few interference fringes, a substrate with a light reflecting film formed by using the mask, a method for manufacturing a light reflecting film, an optical display device having a light reflecting film on which hardly any interference fringes are generated, and an electronic apparatus having a light reflecting film on which hardly any interference fringes are generated.
2. Related Art
As widely known, liquid crystal display devices are widely used as display devices in various electronic apparatuses because of their realization of reduced thickness and the low power consumption. Such a liquid crystal display devices normally have a configuration in which a liquid crystal is injected between a pair of glass substrates and the peripheral edges of the substrates are sealed by a sealant. An electronic apparatus having such a liquid crystal display device therein adopts a configuration in which a protective plate is provided on the viewing side of the liquid crystal display device, that is, on the side toward a viewer observing the display, in order to protect the liquid crystal display device against external impacts. The protective plate is a plate-shaped member which is normally made of a material having light transmittance characteristics, for example, transparent plastic, etc.
However, in such a protective plate, it is difficult to make its surface facing the liquid crystal display device completely smooth, and fine concave portions or convex portions exist on the surface in many cases. Therefore, in the case of providing such a protective plate on the liquid crystal display device, there are many problems such as great deterioration of the display quality due to the fine concave portions or convex portions on the surface.
One reason for the deterioration of the display quality is that the gap between the substrate at the viewing side and the protective plate in the liquid crystal display device is uneven due to the concave or convex portions existing on the surface of the protective plate. That is, interference occurs due to the unevenness of the gap when light coming from the liquid crystal display device passes through the protective plate, and as a result, interference fringes are generated. It is presumed that the display quality is deteriorated because the generated interference fringes and the display images are mixed.
A reflective liquid crystal display device 400 as shown in FIG. 27 is disclosed in Japanese Unexamined Patent Application Publication No. 6-27481; a hybrid reflecting/transmitting type 500 as shown in FIG. 28 is disclosed in Japanese Unexamined Patent Application Publication No. 11-281972, a plurality of concave or convex structures 404a, 404b (504a, 504b) having different heights from each other are provided to decrease the occurrence of interference fringes, high-molecular resin films 405 (505) are formed thereon, and continuous wave-shaped reflecting electrodes 409 (509) are formed thereon.
In addition, a manufacturing process of a liquid crystal display device having such a reflecting electrode is illustrated on FIG. 29, for example. First, as shown in FIG. 29(a), a photoresist film 602 is formed on the overall surface of a glass substrate 600, and then, as shown in FIG. 29(b), the photoresist film 602 is exposed through a pattern 604 being formed of a plurality of different-diameter circles. Then, as shown in FIG. 29(c), it is developed, and a plurality of concave or convex portions 606a, 606b, each having different heights and angles, are provided. Then, by heating the concave or convex portions and softening the angled portion of the concave or convex portions as shown in FIG. 29(d), the angle-removed concave or convex portions 608a, 608b are formed. As shown in FIG. 29(e), an amount of high-molecular resin 620 fills the space between the concave or convex structures 610 to make a continuous layer having the wave-shaped surface. In addition, a wave-shaped reflecting electrode 624 is formed on the high-molecular resin film 620 by using a stacking method such as a sputtering method or the like.
However, although the reflective liquid crystal display device or a hybrid reflecting/transmitting liquid crystal display device disclosed in Japanese Unexamined Patent Application Publication No. 6-27481 etc., employs a mask pattern on which a plurality of different-diameter circles, etc. are aligned uniformly or non-uniformly in part, and intends to provide a plurality of different-heights concave or convex structure by using a ultraviolet exposure and the development, it is difficult to adjust the height precisely to effectively prevent the light interference because of the unevenness of the coating thickness, or the like. In addition, since a reflecting electrode is formed on a plurality of different-heights concave or convex structures, there often occurs a breaking of wire or short-circuited phenomenon, too. In addition, the disclosed method for manufacturing a light reflecting film involves many processing steps and management items to be processed, which results in many problems in the manufacturing.
Therefore, according to the light reflecting films disclosed in Japanese Unexamined Patent Application Publication No. 6-27481 etc., it is difficult to manufacture such a light reflecting film stably and effectively, as well as to prevent the occurrence of interference fringes effectively.
Therefore, there is a method of forming a mask pattern having light-transmitting parts or non-light-transmitting parts aligned randomly, forming a light reflecting film by using that, and manufacturing a reflective liquid crystal display device or a hybrid reflecting/transmitting type liquid crystal display device having such a light reflecting film, but it is presumed that such a method also results in many problems as follows.
1. The random alignment design is complicated in the light-transmitting parts or non-light-transmitting parts, and the mask pattern design is not easy to make.
2. The degree of desirable random alignment in the light-transmitting parts or non-light-transmitting parts of the mask pattern is not assured.
3. The reproducibility of reflecting characteristics of the mask pattern in repeated designs is not assured.
In the meantime, with recent development of a big screen-sized display device such as a liquid crystal display device, etc., mass-production of the display devices having 30 to 40 inches of a display region is being developed, and a 60 inch wall-hanging type display device having 16:9 wide-display screen in aspect ratio is to be developed. In the case of the big-sized display device, there is increasingly required a light reflecting film having few interference fringes generated, while there is also required the easiness or rapidness of the mask pattern design in its manufacturing.
Therefore, as a result after the inventors of the present invention studied the above problems, they discovered that the design of the mask pattern can be easy by allocating the light-transmitting parts or non-light-transmitting parts by a random function, and by using the mask pattern having them randomly aligned over a plane, and furthermore, when it is employed in a liquid crystal display device, etc., the light reflecting film having few interference fringes generated can be achieved easily.
That is, the present invention provides a mask with easy design for achieving a substrate with a light reflecting film having few interference fringes generated when employed on a liquid crystal display device, a substrate with such a light reflecting film, a method for manufacturing such a light reflecting film, an optical display device having such a light reflecting film provided therein, and an electronic apparatus having such a light reflecting film.